The present invention relates generally to a sterilant monitoring assembly for monitoring sterilant concentration levels within a sterilization apparatus. More particularly the present invention is directed to a sterilant monitoring assembly having an external housing defining an internal flow path for sterilant flow therethrough, and an internal housing defining an interior sensor chamber for a sterilant sensor, wherein the interior sensor chamber of the internal housing is selectively in fluid communication with the internal flow path of the external housing.
Aseptic processing of consumable goods, such as nutritional compounds and food products, is typically effected by separate sterilization of the contents and the containers within which the contents are packaged. Subsequent to separate sterilization, the contents are placed in the containers and sealed in a sterile environment for shipment, storage and use.
Sterilization of such containers, which may include separate closures as well, prior to contacting the desired sterilized contents can be performed efficiently by use of a sterilant such as hydrogen peroxide (H2O2) vapor. In such a process, the containers are introduced into a sterilization apparatus in which the containers are flushed with hydrogen peroxide vapor. The containers are subsequently flushed with warm air or any other fluid suitable to achieve desirably low levels of residual hydrogen peroxide. This general procedure is highly effective in achieving sterilization of the containers, and likewise can be performed on any other suitable articles that will come into contact with the desired compound.
Notwithstanding the effectiveness of hydrogen peroxide (H2O2) sterilization, accurate monitoring of H2O2 vapor concentration levels can be problematic. This is due in part to the physical and chemical property changes of hydrogen peroxide vapor under processing conditions, and further due to decomposition upon contact with surfaces of various materials within the processing area. As such, undesired deviation of hydrogen peroxide vapor concentration, and excessive decomposition, can result in loss of sterility of the containers and surrounding aseptic processing area. By contrast, hydrogen peroxide vapor is corrosive in nature, and thus excessive concentration levels can result in detrimental effects to the surrounding equipment and surfaces. Furthermore, and in accordance with government standards, low residual sterilant levels must be maintained for subsequent use of the sterilized containers.
Heretofore, hydrogen peroxide vapor detection systems have been undesirably bulky, as exemplified by conventional near infrared (NIR) analysis apparatus. Additionally, known off-line testing is typically too slow to monitor sterilant levels with sufficient accuracy. Previous arrangements have not provided xe2x80x9creal timexe2x80x9d monitoring throughout an aseptic processing cycle, and particularly have not been capable of monitoring hydrogen peroxide vapor concentrations within the sterilization apparatus at select locations along the sterilant supply system during actual operations.
Additionally, the detected concentration of sterilants such as hydrogen peroxide within a system generally is a function of certain environment parameters, such as temperature and relative humidity, proximate the location of measurement. Conventional sterilant detection systems typically cannot or do not account for local parameter fluctuations. However, such parameter fluctuations can substantially alter signal generation and data collection results using available sensors and equipment. It therefore is beneficial to maintain operating parameters proximate the location of such measurement as uniform as possible during data collection.
In view of the foregoing, it is desirable to monitor the concentration of a sterilant, such as hydrogen peroxide, during sterilization processing. The present invention is directed to a sterilant monitor assembly to be operatively joined to the sterilant supply of the sterilization apparatus. Substantially continuous monitoring of sterilant concentrations can be achieved as sterilant is employed by the apparatus for effecting sterilization of articles therein. Likewise, the present invention enables static testing of sterilant concentration levels and related parameters, as desired or necessary.
The purpose and advantages of the present invention will be set forth in and apparent from the description that follows, as well as will be learned by practice of the invention. Additional advantages of the invention will be realized and attained by the methods and systems particularly pointed out in the written description and claims hereof, as well as from the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, the invention is directed to a sterilization apparatus having a sterilant monitoring system particularly suited to monitor concentrations of the sterilant employed by the sterilization apparatus, such as hydrogen peroxide (H2O2) vapor. The sterilization apparatus generally includes a sterilization chamber and a sterilant supply conduit to supply a sterilant to the sterilization station for sterilization of at least one article thereat. sensor chamber is joined in fluid communication with the supply conduit at a select location to allow at least a representative portion of the sterilant from the supply conduit to flow through the sensor chamber. A sterilant sensor is positioned to provide output signals corresponding to detected levels of sterilant within the sensor chamber. Operatively coupled to the sterilant sensor is a data collection circuit to receive output signals from the sterilant sensor as collected data. In this manner, sterilant concentration levels can be monitored continuously during sterilization processing, with the monitoring system operable to provide a greater degree of correlation between the sterilant levels detected within the sensor chamber and actual concentrations of a sterilant acting upon the articles.
Particularly, the present sterilization apparatus includes an enclosure within which an article conveyor operates to move a plurality of containers or like articles along a conveyor path through the apparatus. One or more sterilization stations are located along the conveyor path. Sterilant, such as hydrogen peroxide (H2O2) vapor in the presently preferred embodiment, is supplied to each sterilization station of the apparatus through a supply conduit for sterilization the articles. For example, the sterilant can be applied in the form of a fog to the external surface of each article at one sterilization station, and injected against the internal surface of each article at a different station. Preferably, the fog applied to the external surface and the vapor injected against the internal surface are applied at different concentration levels to achieve different sterilization values as may be desired.
The sterilant monitoring system of the present invention includes a sensor chamber joined in fluid communication with the supply conduit at a select location to allow at least a portion of the sterilant from the supply conduit to flow through the sensor chamber. A sterilant sensor is positioned to provide output signals corresponding to detected levels of sterilant within the sensor chamber. In the preferred embodiment, the sterilant sensor itself includes a gas-detecting semiconductor element and a heater to elevate the temperature at the gas-detecting semiconductor element. A temperature sensor, such as a thermocouple, also may be positioned to provide output signals corresponding to the ambient temperature proximate the sterilant sensor. Depending upon the type of sensor used, these sensors may be positioned within or integral with a wall of the sensor chamber. The output signals of the temperature sensor are collected in combination with the output signals from the sterilant sensor. Similarly, other sensors to detect operating parameters, such as pressure or relative humidity, also may be provided.
A data collection circuit is operatively coupled to the sterilant sensor, and to the temperature sensor or any other sensor that is provided, to receive output signals from these sensors as collected data. The collected data is processed to provide an output corresponding to the detected levels of the sterilant in the sensor chamber. Processing can be performed by a processor chip or circuit operatively coupled with the data collection circuit at the sensor chamber. Alternatively, correlation between the output signals and the corresponding sterilant levels can be performed by a remote processor located external to the sterilization apparatus. In this manner, signals representative of the collected data are transferred via the data collection circuit by a xe2x80x9chard-wiredxe2x80x9d configuration to the external processor, or via a wireless transfer, such as by near infrared or radio frequency transmission, to a remote communication unit operatively connected to the external processor. Accordingly, the data collection circuit includes a signal connector, such as a data port for physical connection or a transmitter for wireless transfer, to transfer the signals representative of the collected data. The output signals from the sensor, and the corresponding sterilant concentration levels correlated by the processor, can be provided to a suitable display, printer, recording device, or the like.
An electronic memory operatively coupled to the data collection circuit can be provided to create a readable memory of the data collected during a selected time interval. This electronic memory also can be operatively coupled to the internal processor, if provided, to create a readable memory of the correlated sterilant levels as well. A circuit may also be provided as part of the data collection circuit to select conditions for data collection, in combination with a signal connector, such as a data port or receiver, to allow entry of the selected conditions for such data collection.
In accordance with another aspect of the invention, a sterilant monitoring assembly is provided to establish an isolated environment for data collection, as well as enable either continuous monitoring and data collection or static testing as desired. The sterilant monitoring assembly includes an external housing defining an inlet and an outlet, as well as an internal flow path extending therethrough for sterilant flow between the inlet and the outlet. An internal housing is located within the external housing; preferably, the internal housing is substantially surrounded by the internal flow path of the external housing. The internal housing defines an interior sensor chamber therein, and includes a valve arrangement to join the interior sensor chamber selectively in fluid communication with the internal flow path of the external housing. A sterilant sensor, and any other desired sensor of suitable construction, is positioned to provide output signals corresponding to detected levels of sterilant and related parameters within the interior sensor chamber.
Although a variety of valve arrangements can be used, the internal housing preferably includes a base portion and a cover portion moveable relative to each other between an open position and a closed position. In one embodiment, the cover portion preferably is mounted for axial movement relative the base portion, and includes an open end section configured for sealing engagement with an opposing surface of the base portion when moved to the closed position. In another preferred embodiment, the base portion includes a peripheral wall having at least one passageway defined therein, and the cover portion includes a peripheral wall configured to mate adjacent the peripheral wall of the base portion. The peripheral wall of the cover portion has an opening defined therein corresponding to the passageway in the base portion, such that the passageway and the corresponding opening are in alignment with each other when in the open position and out of alignment with each other when in the closed position. In this embodiment, the cover portion preferably is mounted for rotational movement relative the base portion.
In accordance with another illustrated embodiment, a supply manifold is joined in fluid communication with the supply conduit and includes a plurality of flow lines joined fluidly in parallel. Sterilant from the sterilant supply conduit thereby can flow through the plural flow lines respectively to the sterilization station for sterilization of a corresponding number of articles positioned thereat. The conveyor of the sterilization apparatus thus is configured to move a plurality of articles in an array corresponding to the flow lines of the supply manifold so as to allow simultaneous sterilization of a plurality of articles. To detect the sterilant concentration level at the sterilization station, a sensor chamber of the monitoring system is joined in fluid communication with the supply conduit via one of the flow lines of the supply manifold. Preferably, this sensor chamber is joined to an outermost one of the flow lines of the supply manifold; that is, at the flow line located furthest from the supply conduit and thus most likely to have the greatest flow resistance and lowest concentration level within the manifold.
The present invention further contemplates a method of sterilizing articles comprising the steps of providing a sterilization apparatus including a sterilization station and a sterilant supply conduit to supply sterilant to the sterilization station. The method further includes positioning a sterilant sensor at a select location in communication with the supply conduit to provide output signals corresponding to detected levels of the sterilant at the select location, and placing at the sterilization station at least one article to be sterilized. Sterilant is directed through the supply conduit and onto the article placed at the sterilization station, with at least a representative portion of the sterilant from the supply conduit flowing by the select location. The present method also includes the step of generating output signals from the sterilant sensor corresponding to detected levels of the sterilant at the select location.
In the preferred practice of the present method, a temperature sensor is positioned at the select location to provide output signals corresponding to the ambient temperature proximate the sterilant sensor. A data collection circuit is operatively coupled to the sterilant sensor and to the temperature sensor to receive output signals therefrom as collected data. Signals representative of these output signals can be transferred via a signal connector, such as a data port or a transmitter, to a remote communication unit operatively coupled to a processor. An electronic memory may be provided to create a readable memory of data collected during a selected time interval.
The select location for the sterilant sensor may be varied, depending upon the relevant parameters to be monitored. For example, a sensor chamber may be joined in fluid communication with the sterilant supply conduit to monitor overall sterilant concentration levels introduced to the sterilization apparatus. Hence, the generating step includes generating output signals from the sterilant sensor corresponding to the detected levels of sterilant within the sensor chamber.
Using the sterilant monitoring assembly of the present invention as previously described, which includes an external housing and an internal housing with an interior sensor chamber defined therein, the method can include either continuous monitoring or static testing. For example, if continuous monitoring or data collection is desired, the method includes generating output signals from the sterilant sensor while the valve arrangement of the internal housing is maintained in an open position to generate output signals corresponding to detected parameters in the interior sensor chamber of the internal housing. If static testing is desired, the valve arrangement of the internal housing is closed from the open position to capture a static sample of sterilant within the interior sensor chamber of the internal housing. The output signals generated by the sensor(s) therefore will correspond to detected parameters of the static sample of sterilant captured within the interior sensor chamber of the internal housing. This aspect of the invention is particularly beneficial if extended exposure of the sensors to sterilant is to be avoided.
Alternatively, or additionally, the select location may include a flow line proximate a sterilization station of the sterilization apparatus. For example, the sterilization chamber may include a supply manifold joined in fluid communication with the supply conduit, wherein the supply manifold includes a plurality of flow lines joined fluidly in parallel. Sterilant from the supply manifold thus can flow through these flow lines respectively to the sterilization station for sterilization of a corresponding number of articles positioned thereat. The select location of the positioning step of this embodiment is at one of the flow lines of the supply conduit to provide output signals corresponding to detected levels of sterilant. Preferably, the method includes joining a sensor chamber in fluid communication with an outermost one of the flow lines of the supply manifold, with the generating step including generating output signals from the sterilant sensor corresponding to the detected levels of sterilant within the sensor chamber.
Other features and advantages of the present invention will become readily apparent from the following detailed description, the accompanying drawings, and the appended claims.
The accompanying drawings, which are incorporated in and constitute part of this specification, are included to illustrate and provide a further understanding of the method and system of the invention. Together with the description, the drawings serve to explain the principles of the invention.